Temperature is the main factor. Total length of temper time also figures into it. Two hours of tempering time will get you just about all the tempering effects at a given temperature that you're going to get. Some of our hypoeutictic and eutectic steels can get by with one tempering cycle. Your hypereutictic steels may need multiple cycles to get retained austenite to convert. Of course the best thing to do with these steels is not to overheat them and put too much carbon into solution in the first place.

Doug

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If you're not making mistakes then you're not trying hard enough

Not really. It would take hours upon hours upon hours (a day or more???) to significantly drop HRC. The higher the alloy, the more temper cycles. No more than 3 cycles, 2 hours each.

Doug is right, most of the low alloy steels (like 1080) only need a single 2 hour temper. I've even been told ONE hour for simple steels is plenty. The Japanese would only "temper" for a very very short amount of time (not saying that it is right, but they've made millions of very nice kitchen knives using a very short primitive temper method).

For steels like 1080, 1084, 1095, I do two cycles, 2 hours each, just for peace of mind. 52100, O1, O7, CFV steels like that, I treat them as if they were higher alloy stainless and tool steels, and actually do 2 hours each cycle, 3 times. I am certain that is overkill, but it doesn't drop the HRC any.

Blitt at 400 degrees a 2 hour temper would have worked better than heating and cooling it twice. Try it at 400 for two 2 hour tempers. It should be around RC 60 if the austenize heat was in the range to leave the fine grain you said you had. The 5 degree break on .090 thick material is a bit too hard, but how hard do you want it to be? 1080 is a simple steel and if you want flexibility you'll have to temper down properly. As stuart said above you won't hurt it to temper it at the same heat, but one hour tempers are not going to temper it properly. Stuart can explain it better than I.

I temper 1080 at 425 for one temper @ 2 hours, but I haven't used it by itself for a long time except for making Damascus which I prefer to make a little softer like in the RC 57-8 range. I also made two huge daggers and tempered them at 475 because I wanted them to be more flexible as they are for a bear attack or for fighting and breaking isn't an option, but that also means they won't hold an edge as well.

I just googled it up and found redirect hype free blades. It seems that it has been having software problems for awhile and Kevin, with his other obligations and being sole moderator, decided to go in other directions and shut down the board. I don't know if he has other plans for the home site but I think that the board is gone.

Doug

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If you're not making mistakes then you're not trying hard enough